Yes, I know the commercial ones are fairly inexpensive, but what I really want is rubber, not foam. It seems like it would be easy to make a circular half-round groove in a piece of wood or plastic using a router, then apply some mold release and paint it with liquid rubber or 2-part RTV. Strip it out and there's your new surround. Has anybody tried something like this?

Sounds like a fun experiment whatever way it turns out. Give it a go, and report back.

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I have made similar silicone structures in the past. You will need to make a mold and cast it instead, as you can't controll the thickness of the material otherwise.

Counting that little detail out, it's fairly easy and simple to make such. I would go for a sillicone based compound, as you can relatively easy control the hardness of such a compound, and it can be changed by simply changing the propotions of the mix.

Magura

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Hmm... that little detail. I have a mill/drill and rotary table, so making the half round depression is no problem. I'll have to think about how to make the mating half of the mold. There are radius cutters that would do it, first on the ID, then the OD. Same thing can be done with the router, but I don't know how successful I'll be making parts that mate accurately enough to keep the thickness constant. I assume they make the commercial ones the same way, but with better tooling?

Originally posted by Conrad Hoffman Hmm... that little detail. I have a mill/drill and rotary table, so making the half round depression is no problem. I'll have to think about how to make the mating half of the mold. There are radius cutters that would do it, first on the ID, then the OD. Same thing can be done with the router, but I don't know how successful I'll be making parts that mate accurately enough to keep the thickness constant. I assume they make the commercial ones the same way, but with better tooling?

Mill the Negative half flat in the mill first, then cut the groove without disturbing it. Mill the positive haf flat then put a series of holes around the circle in the flat piece and put short screws in. Coat the negative half with release agent. Clean the positive half with the screws. Assemble and fill with epoxy. This sticks over the screws and makes the positive half of your mould.

Use plates of sheetmetal to space the two halves of the mould apart to form your flanges and to allow you to change the thickness by changing the bits of sheetmetal.

While you're at it you may as well add a feathered or patterned inside edge if you're into the Enabl/Mamboni thing.

On further thought that won't work if you go with a full semi-circular shape to the surround. You'll end up with three separate pieces. A slight scallop of about a quarter of a circle should work but you might not get the excusion you want.

Originally posted by Conrad Hoffman Hmm... that little detail. I have a mill/drill and rotary table, so making the half round depression is no problem. I'll have to think about how to make the mating half of the mold. There are radius cutters that would do it, first on the ID, then the OD. Same thing can be done with the router, but I don't know how successful I'll be making parts that mate accurately enough to keep the thickness constant. I assume they make the commercial ones the same way, but with better tooling?

The way to go about it is to use a radius mill and your rotary table. That's the way we did it before CNC equipment became an option.

Make sure you incorporate a couple of cylindrical guides to align the two halves.

Magura

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